Will- You're absolutely right!

Simple 2 channel stereo analog (not bypass) doesn't exhibit it. But if I switch to 6 channel stereo I can hear the hiss increase when I increase the volume. In analog mode but not digital.

Plus, for the 6 channel stereo mode at least, along with an increase in hiss (in my rear center at least, I don't have the other 3 channel amp on), I also get a accompanying increasing in buzzing. (Now I remember someone else mentioning this.)

The plot thickens... So perhaps DSP with analog sources is something to avoid. That'd be kind of rare anyway.